Inner Critic strives to ensure we 'fit in' in hopes of feeling accepted, safe and loved. Since childhood, this part of our psyche has internalized the expectations of our culture, family and friends.
Inner Critic might blatantly attack you, telling you're worthless, ugly, unlovable or a loser. It may also be more subtle by guilt-tripping you into saying 'yes' when you mean 'no,' make you a people-pleaser, or push you to be 'perfect' to get approval and validation.
You may end up resenting yourself and others when you don't get the approval and validation your Inner Critic is relentlessly striving for.